Hydraulic system



April 11, 1961 c. F. SWENSON 2,979,077

HYDRAULIC SYSTEM Filed March 14, 1957 2 Sheets-Sheet l INVENTOR 64?; E JWf/Vjd/V ATTORNLY April 11, 1961 c. F. SWENSON 2, 9,077

HYDRAULIC SYSTEM Filed March 14, 1957 2 sheets-sheet 2 Tlqb.

INVENTOR (iv/a4 F. SWE/ma/V HYDRAULIC SYSTEM Jerse y Filed Mar. 14, 1957, Ser. No. 646,128

4 Claims. (Cl. 137-4933) This invention relates to hydraulic systems, and more particularly to a unitary device which performs the multiple functions of a check valve, relief valve and reservoir for such systems.

In various types of mechanisms, some of the operations are most advantageously performed by hydraulic linkages which, for example, may comprise a master cylinder and an associated slave cylinder, the piston of the master cylinder being actuated by a suitable source of power to produce hydraulic force which causes the piston of the slave cylinder to operate a component of the mechanism. In order to ensure the proper operation of the mechanism under the action of the slave piston, excess pressure generated in the hydraulic system must be accommodated by auxiliary means.

This is accomplished by providing a relief valve which is responsive, or may be adjusted to respond, to a predetermined pressure in the hydraulic system and to transmit excess fluid into a reservoir or the like. When pressure is relieved by the return stroke of the master piston, its cylinder must be replenished with hydraulic fluid, and this is accomplished by providing a check valve which, at a suitable predetermined pressure condition, permits the flow of fluid from the reservoir back to the master cylinder.

In previous systems, the relief valve, the reservoir and the check valve were connected as separate elements to each other by tubing, and as an assemblage, often oc-- oupied a greater amount of space than was convenient to allot in conjunction with hydraulic mechanisms. Also, the multiple junctures of tubing between these elements multiplied the possibilities of leakage, the repair of which interrupted the work time of the apparatus.

The foregoing disadvantages, among others, have been obviated by the hydraulic system of the presentinvention wherein the relief valve, the reservoir and the check valve have been consolidated into a unitary structure requiring only one hydraulic link with the master cylinder, and which occupies a considerably smaller space than previous systems. The invention described and claimed herein comprises a unitary structure in one embodiment of which the relief valve and check valve are positioned substantially coaxially in respect of each other, and which are arranged to perform their respective functions in conjunction with a closed reservoir having a communicating aperture axially aligned with said valves. Also, means are provided for differentiating the respective actions of the relief valveand the check valve as different predetermined pressure conditions obtain within the overall hydraulic system served by the apparatus to be described hereinbelow. Still other-objects and advantages of my invention will be apparent from the specification.

The features of novelty which I believe to be characteristic of my invention are set forth herein and will best the specification and accompanying drawings, in which:

Patented Apr. 11, 1961 Figure 1 is a schematic fragmentary side elevation, partly in phantom outline, of a portion of a line casting machine whose hydraulic system utilizes the combination device of the present invention;

Fig. 2 is a partial section and partial elevation view taken on-line 2*2 of Fig. 1; and

Fig. 3 is a vertical central cross section, greatly enlarged, of the combination check valve, relief valve and reservoir, of the present invention, some parts being shown in elevation.

Referring now to the drawings in detail, Fig. 1 shows a fragmentary portion of a type casting machine to which is atfixed an automatic centering mechanism, generally designated 21, mounted on bracket 22 of the vise frame of the machine. Bracket 22 is pivotally connected at its lower end to horizontal frame bar 23 and is secured at its upper end to upper bracket 24 by means of vise locking screw 25.

Mounted between a pair of vertical castings 26 (Fig. 2) is a master hydraulic cylinder 27 having a piston 28 whose stem 29 extends upwardly through a suitable opening in the top of the master cylinder casing. The lower ends of castings 26 are mounted rigidly on bracket 3% forming a part of the type casting machine.

Secured to the upper end of piston stem 29 is a block 31 having a pair of upwardly extending arms 32 which together support a transverse shaft 33 around which roller 34 rotates between said arms. shaft 33 extend through respective longitudinal slots 35 in castings 26, said slots serving as guides for the reciprocating vertical movements of-block 31.

The upper ends of castings 26 terminate in journals 36 within which the main cam shaft 37 rotates. Mounted fast on shaft 37 and rotating therewith is an actuating cam 38 whose moving peripheral surface bears against the periphery of roller 34, which moves downward and upward in accordance with the contours of cam 38, thereby controlling the vertical movement of'piston 28 by way of block 31 and piston stem 29.

Connected to the bottom of master cylinder 27 is one ice ,end of a tube 41, the other end of which is connected to .the bottom of slave cylinder 42 containing Vertical piston 43 having an upwardly extending stem 44 which pushes against an adjusting screw contained in lug 45 which operates some of the internal elements of centering mech-- anism 21. By means of suitable fittings, tube 41. establishes hydraulic communication between the respective interiors of master cylinder 27 and of slave cylinder 42 whereby the downward movement of piston 28 causes the upward movement of piston 43 when the high lobe of cam 38 bears down upon roller 34. As. cam 38 rotates and pressure is released from roller 34, piston 23 rnoves upward due to a spring return (not shown) actuatmg piston 43 downward thereby causing the hydraulic fluid to flow back to the interior of. cylinder .27 through tube 41. 'Upon the, downward movement of piston 28, lug 4-5 also moves downward by gravity under'the weight of the elements of centering apparatus 21.

Since the upward movement of lug 45 must befully v realized for the proper functioning of the elements in centering mechanism 21, itjis apparent that this can be ensured only by producing-an excess of pressure in master cylinder 27; consequently, .when

upper terminus of its stroke, the excess pressure is accommodated by an apparatus which in the-present invention piston 43 reaches the combines in one unitary structurethe functions of a relief valve, check valve and reservoir. This relief central cross section, may be considered as being symmetrically circular except where otherwise indicated. The

paratusis supported in a casing domounted by suitable means to casting 26. I 1 Y The relieflapparatus, generally'designated .47, and its component elements, as shown in Fig. 3 in longitudinal The outer ends of of the tube.

bottom portion of the apparatus consists of a valve housing 48, made of aluminum, or the like, having a lateral tapped apperture 49 accommodating a threaded nipple 59 which connects said housing with the interior of master cylinder 27.

The inner end of aperture 49 communicates with a central vertical relief valve cavity 53 within valve housing 43, said cavity housing the working components of the ing nut 61 threadably secured into the bottom of housing 48 to close aperture 53. Retaining nut 61 has a pair of inwardly extending recesses 62 which may accommodate the prongs of a spanner wrench for rotating said nut to adjust its position in aperture 53. Nut 61 has an annular recess 63 which accommodates an ring 64 made of a suitable resilient material, such as rubber, or the like, to prevent leakage of fluid from cavity 53.

Retaining nut 61 has a central aperture which accommodates the lower portion of valve piston 54 with a tight sliding fit. Piston 54 has an annular recess 65 which accommodates an O ring 66 made of rubber or the like, to prevent leakage of fluid between the stem and the nut. The top central portion of piston head 55 has a substantially circular recess 67 which accommodates an annul-ar'relief valve seat 68 made of a suitable resilient material such as rubber, Teflon, or the like.

A short distance from the upper end of valve piston 54, its check valve bore 56 has an annular shoulder 71 against which check valve ball 72'abuts under the action of the upper end of check valve spring 73, extending through said bore. The lower end of check valve spring 73 abuts the inner end of retaining screw 74 threadably inserted into the lower end of valve piston 54 and effectively sealing bore 56. Retaining screw 74- has an annular recess 75 accommodating an O ring 76 made of a suitable resilient material, such as rubber or the like, to-

prevent leakage of fluid from the lower end of check valve bore 56. Intermediate its upper and lower ends piston 54 has a pair of transverse apertures 77 which establish communication between relief valve cavity 53 'around the upper side walls of housing'48. The upper end of housing 42% extends a short distance into tube 81 and hasyan annular recess 83 which accommodates an O ring 84- for preventing leakage ofvfluid at the juncture between the reservoir and housing 48. Mounted on top of tube 31 is a reservoir cover 85 having a downwardly extending flange 36 which securely engages the upper edge A circular portion of cover 35 extends downwardly into tube 81 and has a lateral annular recess 87 which accommodates an O ring 88 of a suitable re-' silient material to prevent leakage of fluid therebetween. Y Reservoir cover85 has a'vertical aperture 89 which serves as a fillingport for replenishing the reservoir with bydraulic fluid, Port 89 is engaged by threaded nut 91 having an annular recess 92 which accommodates an O ring 93 for preventing leakage of fluid therebetween.

valve housing 48. Positioned at the upper end of the reservoir and surrounding reservoir stem 95 is a strainer basket 96 made of stainless steel mesh or the like, the upper circular end of which extends beyond port 89 and is urged against the bottom wall of cover 35 by the upper end of retaining spring 97, the lower end of which bears against retaining spring pin 98 extending transversely through reservoir stem 95. Hydraulic fluid poured through filling port 89 must of necessity pass through strainer 96 before it reaches the interior of the reservoir whereby foreign matter is removed therefrom,

The lower portion of reservoir stem 95 has a longitudinal central bore 101 and near its upper end has a plurality of transverse apertures 162 which establish commnnication between said bore and the interior of reservoir tube $1. Extending a short distance into relief valve cavity $3, the lower open end of reservoir stem is abutted by the upper surface of valve seat 63 which is normally urged upwardly by spring 58.

Upon the down stroke of piston 28 in master cylinder 27, hydraulic pressure is transmitted by way of tube 41 to slave cylinder 42 causing the upward movement of piston 4-3 therein.

, Since the extent ofthe vertical motion of lug is variable, depending upon the various predetermined settings established for the internal elements of the automatic centering apparatus 21, it is necessary to insure the full longitudinal motion of said lug for any of said settings, and to provide for a uniform hydraulic pressure throughout each full stroke of said lug. The apparatus is arranged whereby the maximum stroke that may be required by lug 45 is less than the maximum stroke of which the slave piston 43 is capable under hydraulic pressure received from master cylinder '27. Thus, throughout the stroke of the master piston 28, a uniform pressure will be maintained in the system by the relief valve mechanism described hereinabove; and when the slave piston 43 has reached the upper limit of its stroke as determined by the setting for lug 45, excess hydraulic fluid displaced from master cylinder 27 enters through nipple and flows intorelief valve cavity 53 and thence through apertures 77 into check valve cavity 56. I

As the fluid pressure Within cavity 53 increases beyond the pressure limit established upon spring 58 by the position of piston spring retaining nut 61, fluid pressure exerted downwardly 'upon valve seat 68 becomes greater than that exerted upwardly by spring 58 thereby causing the Positioned centrally and longitudinally within tube 81 f is an elongated reservoir stem 95, the upper end of which is threadably inserted into reservoir cover 85 and the lower end of which is threadably inserted into the-top of downward movement of valve piston 54 to open thetlower end, of reservoir stem $5. Thereupon, excess hydraulic fluid flows upwardly into the interior of the reservoir through central aperture 101 and transverse apertures 102 of reservoir stem 95. The fluid pressure necessary to force valve piston 54 downwardly can be predetermined by rotating retaining nut 61 to control the upward force of spring 58. Under these conditions of increasing hydraulic pressure within valve cavities 53 and 56, the fluid is prevented from passing upwardly through the check valve cavity 63 because ball 72 is forced against its seat by the pressure of the fluid assisted by the action of spring 73. Relief valvetpiston 54 operates on the principle of unequal pressure forces. The top surface of piston head 55 exposes a larger surface area to the hydraulic fluid than does the bottom surface of annular shoulder 57. Consequently, when a predetermined pressure condition in valve chamber 53 is exceeded, piston54 will be caused to movedownward against the action of spring 58.

Upon the upward return stroke of piston 28 in master cylinder 27, thereby resulting in negative pressure created check valve cavity 56, through apertures 77 into relief valve cavity 53 and thence through nipple 53 to master cylinder 27 to enable the latter to repeat its control function as described hereinabove.

In the specification, 1 have explained the principles of my invention, and the best mode in which I have contemplated applying those principles, so as to distinguish my invention from other inventions; and I have particularly pointed out and distinctly claimed the part, mode or combination which I claim as my invention or discovery.

While I have shown and described certain preferred embodiments of my invention, it will be understood that modifications and changes may be made without departing from the function and scope thereof, as will be clear to those skilled in the art.

I claim:

1. Hydraulic apparatus comprising a housing, an elongated chamber in said housing, an inlet port in said housing communicating with said chamber, an outlet port in said housing communicating with one end of said chamber, said outlet port being axially aligned with said chamber, an elongated relief valve member movable within said chamber, a valve seat in said chamber at said outlet port, one end of said relief valve being adapted to cooperate with said valve seat, a cylindrical retaining nut at the other end of said chamber, a first spring positioned between said nut and a portion of said relief valve, said spring normally urging said relief valve against said valve seat to close said outlet port, said relief valve being movable away from said seat against the action of said first spring when fluid pressure within said chamber exceeds the force of said first spring, said relief valve being movable longitudinally within said retaining nut, an elongated check valve cavity positioned axially within the interior of said relief valve member, a relief port at one end of said valve member establishing direct communication between said check valve cavity and said outlet port, a retaining screw positioned in the other end of said check valve cavity, a movable check valve in said check valve 6 cavity, a second spring positioned between said retaining screw and said check valve normally urging said check valve against said relief port and at least one lateral port in said relief valve member establishing communication between said check valve cavity and said chamber.

2. Hydraulic apparatus according to claim 1, and further comprising a reservoir adjacent said housing, a tubular reservoir stem extending through said outlet port and establishing communicationbetween said chamber and said reservoir, one end of said stem extending at least partially into said chamber, the end of said stem in said chamber forming the valve seat with which said valve member cooperates.

3. Hydraulic apparatus according to claim 1 wherein said retaining nut is adjustable in position for establishing a desired tension upon said first spring.

4. Hydraulic apparatus according to claim 1 wherein said retaining screw is adjustable in position for establishing a desired tension upon said second spring.

References Cited in the file of this patent UNITED STATES PATENTS 481,001 Hendrick Aug. 16, 1892 1,107,383 Udstad Aug. 18, 1914 1,651,971 Shield Dec. 6, 1927 1,954,534 Norton Apr. 10, 1934 2,014,338 Messier Sept. 10, 1935 2,112,356 Bock Mar. 29, 1938 2,166,742 Lambert July 18, 1939 2,393,589 Compton et a1 Ian. 29, 1946 2,565,094 Roy Aug. 21, 1951 2,597,404 Teske May 20, 1952 2,665,708 Ghormley Jan. 12, 1954 2,865,396 Focht Dec. 23, 1958 OTHER REFERENCES Harten: German application Ser. No. H19085Ib/49h, October 18, 1956 (K1. 49h, 1701). 

